The open-plan office was the first threat to private conversations of workers who found themselves whispering into their phones.

And the advent of the energy efficient ''green building'' with its eerily silent surrounds, free from the incessant hum of machines, was the death knell. As various studies show, we are most irritated by intermittent sounds, which is why we can handle whirring fans but not barking dogs or pen-tapping colleagues.

But there is a solution. It is called ''sound-masking'', which introduces artificial background noise to ''mask'' conversations. It works by pumping artificial sound which creates a general hum into a room from multiple speakers, spaced three to five metres apart, that are secreted in the ceiling or under the floor.

Graham Alderman, the managing director of Australian Sound, says sound-masking systems are becoming more popular.

''It's [still] not something that is an automatic inclusion … but they're starting to appear in consultants' specifications, more so than they ever did,'' Mr Alderman said.

''Most of these things now appear to be in green buildings … previously they've been in courts and anything to do with the legal fraternity, where they try to mask conversations.''

This year, Mr Alderman's company won an industry award for its work at the ANZ headquarters in Melbourne's Docklands, where it installed 4000 speakers.

Kieran Drea, an installer for Soundmask Australia, said sound-masking systems were now in some of Sydney's most recognisable buildings such as the Macquarie Bank building in King Street Wharf and the ticket booths at the Opera House. Mr Drea said he had just installed a system at the futuristic Commonwealth Bank building in Darling Harbour.

''Their popularity has been increasing because with open-plan offices, call centres … if the acoustics in a building are not right [workers] have no privacy,'' he said.

''By putting in the sound-masking system, it actually gives them more protection. You can still hear people talking but you won't be able to understand their conversations.'' Mr Drea said the systems were also installed in lawyers' chambers, doctors' waiting rooms, and even schools.

But Julian Treasure, a sound expert in Britain, said he did not like the idea of adding artificial noise.

''I am not a fan of masking to cover up noise … But masking may be required in very quiet rooms to create privacy,'' he said.

''[If you need to do so] I would suggest using natural, stochastic sound like birdsong or running water rather than artificial sound … That way you get the best of both worlds: effective privacy plus a pleasing soundscape that fosters productivity.''